Similar results were found in a prospective study of more than 25,000 Norwegian men (Int J Cancer, 1997; 73: 634-8) and, in an analysis of milk-drinking and diet in 41 countries, Dr William B. Grant, of the NASA Langley Research Center in Virginia, found that non-fat milk had the highest association with prostate-cancer death rates (Altern Med Rev, 1999; 4: 162-9).

Calcium unbound
Thus, rather than being a healthy choice, low-fat milk-and possibly other low-fat dairy items-may, in fact, be detrimental to men's health. But why should this be so?

One theory is that removing the fat from milk strips it of certain nutritional components that are vital to health. Fat is found in milk for a reason. It contains vitamins A and D, both of which are necessary for the uptake and use of the calcium and protein elements in milk. Without these vitamins, milk protein and calcium are more difficult to absorb-and can even become toxic to the body.

Calcium, particularly in large amounts, seems to have a specific adverse effect: it suppresses the formation of calcitrol, the hormonal form of vitamin D. Because calcitrol has anticarcinogenic effects on prostate cells, scientists have postulated that a reduction in the amount of calcitrol in the circulation could increase the risk of prostate cancer (Anticancer Res, 1990; 10: 1307-11).

Indeed, a recent study from Harvard showed that a high calcium intake-whether from diet or supplements-was associated with reduced levels of calcitrol and a higher risk of prostate cancer (Cancer Epidemiol Biomarkers Prev, 2006; 15: 203-10). The above-mentioned Finnish study also suggested a connection between calcium and prostate cancer (Int J Cancer, 2007 Feb 2; Epub ahead of print).

While the suppressive effects of calcium from whole milk may be countered by higher levels of vitamin D, such a reversal of calcium effects may not occur with low-fat milk as fat-reduced milk tends to contain little, if any, vitamin D. And even if the vitamin is added to skimmed milk, as it is in the US, it may still be less well-absorbed from fat-reduced milk.

This has been confirmed in studies looking at different types of milk that have shown that calcium from low-fat or skimmed milk is associated with a greater risk of prostate cancer, while calcium from whole milk is not (Am J Clin Nutr, 2005; 81, 1147-54; Am J Clin Nutr, 2001; 74: 549-54). So, it appears that, far from being good for us, calcium-when separated from the fat in milk-can be toxic to the body.

The CLA connection
Another possible explanation is that stripping the fat from milk also removes other important cancer-protective components such as conjugated linoleic acid (CLA). CLA was identified as a component of milk and dairy products over 20 years ago, and studies have shown it to be a powerful anticarcinogen. In the lab, when human breast and colon cancer cells were bathed in high-CLA milk fat from cows raised on pastureland, the number of cancer cells was reduced by 58 per cent up to 90 per cent (Br J Nutr, 2003; 90: 877-85; Anticancer Res, 2000; 20: 3591-601).

Although modern milking methods and processing affect the CLA content of milk, women who consumed four or more servings a day of high-fat dairy foods were half as likely to develop colorectal cancer as women who ate less than one serving a day; low-fat dairy had no effect. The researchers attributed the results to CLA, although they noted that other potentially anticancer components, such as sphingomyelin and ether lipids, may have also played a role (Am J Clin Nutr, 2005; 82: 894-900).